73-87 Chevy _ GMC Trucks > Fuel Systems and Drivability

Evap Canister, hose routing, simplification at all?

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So I finally had some time and was working on my C10 (1985, 305, TH-350C).  I'd like to simplify all of the craziness around the vac lines to the evap canister.  They tee into each other so much, it is hard to tell what's going on. I replaced some of the lines which were shot when I got the truck to try to cut down on vac leaks. 

My question is, is there anything I can do to simplify some of this?  My Olds projects often have just one or two connections to the vac canister, so I feel like something simpler should work.  The C10 has this crazy set of lines which seem to tee into each other a lot and I get the feeling that not all of those connections are leak free.

The truck has to pass an emissions test (sniffer) and they always check the gas tank holds pressure. The clamp off the line marked with the red arrow which is the vapor line from the tank. I don't think they check anything else.

Can I remove or cleanup some of the hoses that route to the canister?  I think the one on my Olds is hooked up to ported vac on the carb and that's about it...

I am also adding in the hose routing as best as I can.  If you look closely, I marked the two larger bore hoses blue and green to try to make it more visible.

One goes through the PCV valve tee and direct to manifold vac. The other goes to the air horn of the carb.  Not sure if that's exposed to vac or not.  Either way, I have no idea if this is how things are supposed to be or if the previous owner did some "creative routing" with the hoses.

Looks like someone did something, there are hoses missing from the vac valve on the T-stat housing... :o

If all your state does is sniff and does not care about visual inspection, then I guess you can move on without restoring the correct circuits.

I would find a diagram of your truck's vac circuit and then make the determination if a PO did some funny stuff.

BTW, my first resto was a '67 Olds Toronado. What a blast for a 22 year old! Rocket 425 V8! I've also done a '66.

Thanks for responding.  I missed it initially.

Yeah, that was me, actually.  I took the pictures while I was re-routing some wiring and replacing a broken plastic vac line (down to the EFE valve in the passenger's exhaust) and I had the 4-port connector off of there.  It is back now.  :)

I guess I was just wondering how all of this was originally intended to work and why there is so much "stuff" connected to it when my Olds' have always had such a simple hookup from the factory.  Feel like it should need just vac and maybe ported vac signal to keep it closed while you are at idle...

Toronado's are a love / hate for a lot of people. The front-drive with standard engine mounting are just not always liked. Personally, I think they are cool cars and the transmission setup has proven reliable enough. I've helped a local guy with his 68, but have never done one myself.

Hi OldsFan,

What did you end up doing? I'm installing an evap canister where there was none when I purchased the truck. I don't need to pass emissions, I just don't like the gasoline smell in the garage.

The vacuum from the pvc is tee'ed to the purge? Was it house the whole way or tube part of the way?


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